1. Field of the Invention
The present invention relates to a control system for switching a traveling state between a two-wheel-drive traveling state and a four-wheel-drive traveling state in a four-wheel-drive vehicle that includes a clutch mechanism disposed closer to a driving power source than a driving power transmission shaft and right and left clutches disposed in power transmission paths to right and left wheels as secondary drive wheels.
2. Description of Related Art
A four-wheel-drive vehicle is well known which includes a connection and disconnection mechanism disposed on a driving power source side of a driving power transmission shaft (for example, propeller shaft) that transmits dynamic power to secondary drive wheels, which serve as driven wheels at the time of two-wheel-drive traveling (2WD traveling), at the time of four-wheel-drive traveling (4WD traveling) and right and left clutches disposed in power transmission paths to the right and left wheels of the secondary drive wheels, respectively, so as to control a transmission torque. An example thereof is described in U.S. Pat. No. 8,313,407 B2. In the four-wheel-drive vehicle, by disengaging the connection and disconnection mechanism and the right and left clutches in a 2WD traveling state in which dynamic power is transmitted to only primary drive wheels for traveling, it is possible to stop rotation of rotation elements (such as the driving power transmission shaft) constituting a part of the power transmission paths between the connection and disconnection mechanism and the right and left clutches. In this case, it is possible to improve fuel efficiency compared with a case where only one of the connection and disconnection mechanism and the right and left clutches is disengaged in the 2WD traveling state.